View Full Version : Degassing Co2
I posted in the DIY section that I've made a degasser using a 3ft bubble lamp, and I've now got it up and running okay with the original air pump pushing up a good quantity of air through the media. I'm currently running it with the same P25 (?) media as I use in the Ca reactor. My question is, would I be better off using dolomite in the hopes of getting some Mg into the system too? There is an old topic here that suggests that possibility but I'd like to know if its a practice used by anyone, and what effect is has had on boosting their Mg?
I find dolomite very hard to dissolve. It needs pH down to around 6.0ish so in a second chamber you probably won't get that much of a result.
tuan. I noticed in simonh's article on reactors the same suggestion you (I think) made some short while back - that dolomite can be added to the reactor's media to produce Mg. In that article he talks of the reactor's pH being around 6.5. I also read somewhere here you suggesting some other media. Can you recall what that was and perhaps what pH is required to dissolve it?
I'm not sure what you're after. I use dolomite in the reactor to add some Mg back into the system (hence reactor is running at pH 6.0-6.1).
As a second chamber media, I currently use rowadur, which has a much higher melting point. At next change I will probably switch over to ARM as the effluent pH from the first stage is still 6.1ish so should be sufficient to add melt some of the ARM.
Rowadur. That was the stuff. If that has a higher melting point than dolomite it won't be much good to me right now. What is ARM?
Rowadur is a mainly calcium carbonate reactor media made by Rowa and distributed by D-Deltec.
ARM is Aragaonite Reactor Media and is mined and distributed by Carib-Sea.
Dolomite (magnesium carbonate, MgCO3) can be useful for replacement of magnesium used in calcification (coralline algae etc.) if your media isn't supplying enough. However, it is no use for raising your magnesium levels if they are already low due to salt mix etc. For every 12ppm of magnesium added to your system the alkalinity rises by around 1 mEq/L.
Tuan,
Wait until I tell Mr Hipkiss about you "melting" calcium carbonate ;) :D
Simon. I have Mg Chloride which I use now and again but when I heard that dolomite can release Mg naturally I thought I'd investigate the possibilities of using it as the degasser media as opposed to the reactor's. From what I read, this won't work unless the pH is around 6.
Originally posted by simonh@Apr 13 2004, 10:47
Tuan,
Wait until I tell Mr Hipkiss about you "melting" calcium carbonate ;) :D
No please... I beg of you... :bow:
:lol:
Kevin Douglas
14-04-04, 07:30
Robin,
Carabsea ARM would be ideal for your application as it releases Magnesium as well. I use ARM in my Reactor and find it keeps my Magnesium at 1350 plus.
It does say on the box it dissolves a 7.50 pH but I have not found this to be true.
It needs 6.40 to 6.50 pH.
Atb
Thanks Kevin. I'll give it a whirl.
The ARM media is too fine for the fast flow reactor such as the Schuran Jetstream 2. You can use it but you should fill the top half with a heavier large grain media like the AquaMedic Hydrocarbonate (largest size).
Otherwise grains/bits will get sucked into the pump and cause havoc with the venturi.
tuan I was working on putting it in the degasser! Still the same pH?
Kevin Douglas
14-04-04, 13:35
I did not mean for you to put it in the Schuran. I agree with Tuan the flow would be to much. Glad you realised that Robin.
Atb
Oops - forgot what we were on about, duh! :blush:
Actually, I'm setting up a secondary reactor just to run ARM this way, so this reactor (probably a knop C) will be fed from the effluent of the JS2 (which is about pH 6.1 ish), and hopefully I can dissolve some of the ARM to add Mg.
Tuan. Why a second Ca reactor for the ARM? Why not use that media in a degasser (or second) chamber directly off the Schuran? The pH coming from the Schuran should be the same going into the second chamber, should it not? I ask because thats my intention this weekend - to fill the second chamber (degasser) with ARM. Solves the problem of shafting the 1060, doesn't it?
The second reactor will be the 'degasser', as a second chamber, but I'm thinking that with a circulation pump as well it would be a bit more efficient. Possibly another option is to have a large chamber (like a salt bucket) and fill it with coral sand and let the slow flow through do the work for you.
Rightly or wrongly I run air up from the bottom of my degasser. Maybe that gives sufficient circulation without the need for a circulation pump that might get blocked?
I no longer think running an air bubbler is a good idea. A lot depends on how saturated the effluent is with Ca, but essentially as the pH rises some of the Ca ions you've put in the effluent will precipate out of solution, especially if there are nice surfaces like the grains of the media to provide crystalizing sites.
My aim for the second chamber is try and dissolve some more media and fully saturate the solution. Any excess dissolved CO2 in the effluent will soon get used up as it hits the tank by the limewater additions.
Just found a thread about this ages ago:-
http://www.reefcentral.com/forums/showthre...chamber+reactor (http://www.reefcentral.com/forums/showthread.php?s=&threadid=31712&highlight=degas+second+chamber+reactor)
Thanks for the thread. I'll compare the pH and Ca from entry to exit of the degasser with and without air.
Turns out the air was costing me a pH increase of 0.75. :(
What about the Ca/Alk readings? Any significant drop?
The increase in pH is desirable if not too much is lost via precipitation.
tuan I can't say - for a while. To hopefully rid the tank of the algae I've now stopped Co2 input altogether although I'm still running a water flow through the reactor (rather than empty it). Kalk is still being added via the top off. I'm hoping the algae will die back and then I'll restart the Co2 at a sensible level. :thanx:
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